1. Field of the Invention
The present invention relates to an AC generator to be installed on a vehicle such as automobile and, more particularly, to an improvement in the cooling mechanism of the generator.
2. Description of the Prior Art
In the conventional generator of the class specified above, a cooling fan is mounted on a rotor shaft and driven to produce a flow of cooling air which is introduced into the motor housing through air inlet openings in the rear end wall. The air then flows through spaces between respective fingers of the rotor core and also through the gap defined between the rotor core and the stator and is discharged out of the motor housing through air outlet openings formed in the front end wall of the housing.
As discussed, the prior art AC generator is so designed that the cooling air flows through the narrow air gap and through the spaces between the fingers of the rotor core. Thus, the resistance to the air flow is so high that the rate of the cooling air flow is not sufficient to surely and reliably cool the heat-generating components of the motor, such as the diode fins, stator coil and rotor coil, with a result that the performance of the generator is lowered.
As a solution to the problem pointed out above, a centrifugal or radial-flow fan can be mounted on one end face of the rotor core to produce a flow of air that passes across the stator coil. This solution, however, falls short of satisfactorily solving the problem in that the cooling air flow is not directed to the rotor coil and thus the rotor coil cannot be cooled.